IRON. 



311 



Iron, rent parts of the blowing apparatus, worked by a steam 

 , ' engine. ^ ^ 



In the first a = , and in the second a = . 



n v v \ 

 Hence -T- = 

 I P 



*""* 



1st, A = ' 



'=<=" 



4th, p = 

 5th, n = 



AS/ 



" ~-" 2 

 i- n 



AS/ 

 ~P^' 



AS 

 a 

 al 



al 



SA 



e, in common language, to find the area of the 

 steam cylinder, multiply the pressure of the blast, the 

 velocity, and the area of the nose-pipe together ; and 

 'o the product by the pressure of the steam upon 

 an inch multiplied into the velocity of the piston ; 

 which is in most steam engine* 200 feet in a minute, or 

 3 feet 8 inches per second. This will enable the reader, 

 unacquainted with algebra, to get the value of the other 

 ti theorem*. 



It will be understood that the steam piston, and that 

 of the blowing cylinder, are at opposite ends of the 

 same beam, one amending a* the other descends ; the 

 area of the steam cylinder bearing the same proportion 

 to that of the blowing cylinder, which the pressure up- 

 on an inch of the steam bean to the pressure of the 

 blast upon an inrh. 



The air is not immediately discharged from the blow. 



ing cylinder into the furnace, but into sn intermediate 



cylinder, of larger diameter, called a regulator. In 



this vessel is a loote piston, which is forced up by the 



air li' i the blowing cylinder, and being weighted, it 



> ml* ilunnj; the returning stroke, and continues to 



the air into the furnace, by which means a more 



steady and uniform blast is kept up than would be 



fected l>y the r ler alone. 



Although this method of regulating the blast i> in 



- very far from being perfect. 



Another means hais been employed for this purpose, 



*inting of an apparatus called water regulator 



is composed of a large cistern, in which another of less 



area and capacity is invested ; the mouth of the latter 



is placed downwards and the bottom upward-., which is 



air tight. Supposing this interior vessel filled with wa- 



ter, occupying at the same time the space between the 



r .md outer vessel. It is plain that if air be forced 



the inner vessel through a pipe inserted into its in- 



verted bottom, the water will descend in the m: 



se), bring di-pUced by the air ; snd it will rite up be- 



tween the two vessels, till the column of water on the 



outside shall be equal to the required force of the blast. 



column, in the furnace above mentioned, would 



be equal t producing 4tb upon an inch, and would be 



> of S4, or about 9 feet- Another pipe proceeds 



from the same cavity in the inner vessel to the furnace, 

 communicating nearly a uniform blast, varying merely 

 with the outer column of water, which will be less, as 

 the outer surface of the water is greater. the blast." 



This contrivance was for some time considered an 

 important discovery, but unfortunately another circum- 

 stance has also rendered it very objectionable. A quan- 

 tity of water is carried into the furnace, as well in the 

 state of vapour as mechanically, the latter arising from 

 the spray produced by the agitation. This water has 

 been found to have an effect upon the furnace, affect- 

 ing both the quantity and quality of the iron ; and has 

 been in many instances abandoned, to re- adopt the old 

 regulations. 



Another means has been employed to equalize the 

 blast, by what is called an air-vault This consisted in 

 blowing the air into a very large cavity. The experi- 

 ment was first tried at the Clyde iron works, by exc.i- 

 rating a large cavity in a rock, into which the air was 

 forced by the blowing machine. This capacity bore so 

 great a ratio to the blowing cylinder, that the blast out 

 of it was nearly uniform. This trial was not attended 

 with success, partly from the vault not being air tight, 

 and partly from the moisture which exuded from the 

 rock mixing with the air. 



A more successful experiment was made at the Car- 

 ron iron works. An air- vault of wrought iron plate has 

 been employed in one of the furnaces at Bradley in 

 Staffordshire, which appears to answer very well. lu 

 form is a cylinder about 10 or 12 feet diameter, and 50 

 or 60 feet long. Since the object of blowing air into 

 the furnace is to produce heat, the heat being as the 

 quantity ; therefore the quantity which enters in 

 given time, will be as the velocity and the density joint- 

 ly. If, howevsjr, the dei he air depends up- 

 on the compression, the propelling force will l>c in- 

 creased, and the air is drawn into the furnace with too 

 great a velocity. The cementing portion of the furnace 

 is less perfect from the oxygen being carried too high 

 up before it combines with the carbon, and the mate- 

 rials would be apt to disunite before the proper change 

 is produced. 



Hence it will be evident, that when the density is 

 caused by its being introduced at a lower temperature, 

 the velocity remaining the same, and such as is found 

 to be free from the objection above stated, the effect of 

 such a bint must be calculated to produce the best iron, 

 Mid the greatest quantity of it. This, in a great mea- 

 sure, explains the fact of more iron, and of better quality, 

 being made in winter than in summer. The same dif- 

 ference is not less conspicuous in all fires, which al- 

 ways bftn most vigorously in cold weather. Hence 

 ' appear, that in blowing apparatus, all cause* like. 

 Ijr K> increase the temperature of the air should be avoid- 

 ed, and every artificial means of cooling the air should 

 be employed, particularly in the summer. 



In the common blowing apparatus, in which the air is 

 compressed by al close wadded piston, a great heat is 

 produced in the operation. This is partly produced by 

 the condensation of the air, and some heat must result 

 from the Iriqfion of the piston. In some experiments 

 made by Mr. D.ivid Musheti, it appears that when the 

 outer air was from 63" to 68', the air immediately after 

 its escape from the blowing cylinder into a receiving 

 vessel, was increased from 63 to 90", and from 63 to 

 994. In an average of 30 experiments, the air in the 

 act of condensing was raised 30. This would have the 

 effect of increasing its volume not less than ,', of i'ic 

 whole, and the increased pressure of the blast by th's 



